Closed-captioning is the synchronized display of textual data with the underlying video program. In other words, closed-captioning allows a program viewer to see the video image on screen, while simultaneously reading the underlying dialogue instead of having to hear it. Traditional techniques for adding closed-captions to video data require expensive, special-purpose synchronization software and encoder hardware.
The closed-captioning of video programs is typically done in two stages. In the first stage, an enhanced dialog text script is created in a word processor and an association is made between each piece of text and a specific time sequence within the video program during which the text is to be displayed. This synchronization process is typically done by a skilled technician using a computer and associated software to associate a time code to the desired text.
In the second stage, the time-coded closed-caption data is merged with the underlying video program. Prior art methods of merging the closed-captioning and video image data require the use of dedicated and expensive closed-captioning systems. See FIG. 1. These systems include separate hardware, typically referred to as a closed-caption encoder 3. In a typical prior art system, the encoder 3 accepts a video signal from a playback VCR 2 playing a master video tape and simultaneously accepts from a computer 1 the closed captioning instructions created in the first stage. When the encoder 3 recognizes the appropriate time code it formats the associated textual/closed-caption data according to the Electronic Industries Association Standard EIA-608, Recommended Practice for Line 21 Data Service (incorporated by reference herein), and superimposes the formatted data onto the video data stream emanating from the master tape. A record VCR 4 records the output of the encoder. In this manner, the closed-caption data is placed onto line 21 of Vertical Blanking Interval (VBI) of the video data signal by the encoder. The resulting output video tape is designated as a close-captioned encoded submaster video tap.
The U.S. Federal Communications Commission specified through the Television Decoder Circuitry Act of 1990 (Decoder Act) and subsequent FCC legislation that all television receivers imported into the United States or sold in interstate commerce after Jul. 1, 1993 with a screen size greater than 13 inches must be capable of decoding and displaying closed-captions. The Decoder Act and corresponding regulations were put into effect to make closed-captions more readily available to the hearing impaired and to provide the television broadcast industry with an ever expanding base of closed-caption capable television receivers.
From a slow beginning closed-caption programming has gradually gained momentum to a point where television programming that contains closed-captioning is the norm. Prior to the development of the present invention, a video production house desiring to add closed-captioning to its program had three options. First, the production house could send a master tape of its program with the dialog script to a third-party closed-captioning company. Second, the production house could purchase closed-captioning software and generate the commands required to drive a hardware encoder that is operated by a third-party closed-captioning service. Lastly, the production house could purchase expensive closed captioning equipment and perform the entire closed-captioning process itself.
Faced with this type of up front capital expenditure and the costs of the various closed-captioning options, it is desirable to find an alternate way of close-captioning a video program. Furthermore, since the use of the vertical blanking interval for the transmission of other control data, such as Content Advisory information and Uniform Resource Locator information in Interactive Television programs, is becoming more widespread, an effective and inexpensive method and apparatus are needed to add such control data to the underlying video image data.